title: Synthesis and transistor properties of asymmetric oligothiophenes: relationship between molecular structure and device performance.
abstract: A series of three thiophene-naphthalene-based asymmetric oligomers-5-decyl-2,2':5',2'':5'',2'''-quaterthiophene (DtT), 5-decyl-5''-(naphthalen-2-yl)-2,2':5',2''-terthiophene (D3TN), and 5-(4-decylphenyl)-5'-(naphthalen-2-yl)-2,2'-bithiophene (DP2TN)-was synthesized by Suzuki cross-coupling reactions. The long alkyl side chains improved both the solubility of the oligomers in solvents and their tendency to self-assemble. UV/Vis absorption measurements suggested that DtT, D3TN, and DP2TN form H-type aggregates with a face-to-face packing structure. In addition, the three oligomers were found to adopt vertically aligned crystalline structures in films deposited on substrates, as revealed by grazing-incidence wide-angle X-ray scattering. These oligomers were used as the active layers of p-type organic field-effect transistors, and the resulting devices showed field-effect mobilities of 3.3×10(-3)  cm(2)  V(-1)  s(-1) for DtT, 1.6×10(-2)  cm(2)  V(-1)  s(-1) for D3TN, and 3.7×10(-2)  cm(2)  V(-1)  s(-1) for DP2TN. The differences in transistor performances were attributed to the degree of π overlap and the morphological differences determined by the molecular structures.
authors.affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, POSTECH Organic Electronics Laboratory, Polymer Research Institute, Pohang, 790-784 (Korea).
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: An
authors.forename: Sang Hun
authors.initials: SH
authors.lastname: Jang
authors.forename: Seul-Ong
authors.initials: SO
authors.lastname: Kim
authors.forename: Jaeyoung
authors.initials: J
authors.lastname: Jang
authors.forename: Jihun
authors.initials: J
authors.lastname: Hwang
authors.forename: Hyojung
authors.initials: H
authors.lastname: Cha
authors.forename: Young Ri
authors.initials: YR
authors.lastname: Noh
authors.forename: Soon Byung
authors.initials: SB
authors.lastname: Yoon
authors.forename: Yong Jin
authors.initials: YJ
authors.lastname: Yoon
authors.forename: Lae Ho
authors.initials: LH
authors.lastname: Kim
authors.forename: Dae Sung
authors.initials: DS
authors.lastname: Chung
authors.forename: Soon-Ki
authors.initials: SK
authors.lastname: Kwon
authors.forename: Yun-Hi
authors.initials: YH
authors.lastname: Kim
authors.forename: Sang-Gyeong
authors.initials: SG
authors.lastname: Lee
authors.forename: Chan Eon
authors.initials: CE
authors.lastname: Park
keywords: aggregation; oligothiophenes; semiconductors; thin films; transistors